1. Field of the Invention
The present invention relates to an image input apparatus of a video conferencing system.
2. Related Background Art
Video conferencing systems using personal computers are known, such as PCS100 and PCS50 from Picture Tel Corporation and Proshare from Intel Corporation. Such personal computer based video conferencing systems are also called a Desk Top Video Conferencing System (DTVC).
DTVC is now highlighted as a downsized version of a conventional video conferencing system which is configured basing based upon a video monitor and designed for use in a conferencing room. FIG. 5 is a block diagram of DTVC designed by present inventors. In FIG. 5, reference numeral 101 represents a video camera, reference numeral 102 represents a video board having an image pickup function and a data compression function, reference numeral 103 represents a communication board interfacing with, for example, an ISDN line, and reference numeral 104 represents a floppy disk for storing video conferencing software.
The video board 102 and the communication board 103 are expansion boards for personal computers and are inserted into expansion slots of the personal computers. FIG. 6 is a perspective view of a personal computer with the video board 102 and the communication board 103 being inserted into expansion slots and with the video camera 101 being mounted on a monitor 108 of the personal computer. Reference numeral 105 represents the main body of the personal computer, reference numeral 106 represents a mouse, and reference numeral 107 represents a keyboard.
The floppy disk 104 with video conferencing software is inserted into a disk drive of the personal computer 105 and an operator enters necessary commands to load the video conferencing software into a hard disk (not shown) of the personal computer.
After the video conferencing software is loaded, it is activated by entering necessary commands. Then, an image (LOCAL) of an operator is picked up with the video camera 101 and displayed on the screen of the monitor 108. FIG. 7 illustrates an image of the operator displayed on the monitor 108.
A remote side is called, for example, via an ISDN line by entering necessary commands. After preset connection operations, an image (REMOTE) of the partner is displayed on the monitor 108. FIG. 8 illustrates the images of the operator (LOCAL) and the partner (REMOTE) displayed on the monitor 108. In the above manner, video conferencing is made between the two participants.
How voices at video conferencing are processed is not relevant to this invention, and so the description thereof is omitted.
With the above video conferencing system, however, the video camera is used on the assumption that it always picks up moving images. There are the following problems of picking up still images.
Two methods have been used in taking a still image. Each method is associated with a problem specific to it. With a first method, a still image is taken in a moving image mode. The video camera 101 shown in FIG. 6 is dismounted from the monitor 108 and mounted on a document pickup stand to take an image of a document. In the moving image mode, an image is transmitted in accordance with the ITU-T International Standards, for example, a protocol stipulated by H320. A moving image containing video and audio signals is transmitted at a transmission rate of 64 Kbps (56 Kbps in USA) of a general ISDN line. A moving image is compressed greatly at about 1/100 to 1/200 by using interframe correlation for moving image compensation stipulated by H261. A still image picked up by this compression scheme gradually increases its resolution in several seconds to ten and several seconds.
Therefore, after transmission of a document during a video conference, it takes about 10 seconds to clearly recognize characters. This is inconvenient to use. Furthermore, the image quality after 10 seconds is inferior to that of JPEG compression dedicated to still images. The quality of a still image has been desired to be improved.
With a second method, a still image is picked up in a still image mode. The video camera 101 shown in FIG. 6 is dismounted from the monitor 108 and mounted, for example, on a document pickup stand. A still image pickup mode of software is selected, for example, by clicking a mouse to freeze a still image.
Since data compression dedicated to still images can be used, there is no problem of image quality. However, mouse clicking or the like is required in addition to framing of the video camera. This poses a problem of difficult operations by a user. This problem becomes conspicuous, especially when the video camera is not mounted on the stand but is held with a hand. It is very difficult to operate a mouse with a right hand while the video camera is held with the left hand.